The intracoronary administration of the parasympathomimetic drug, carbachol, has been shown to increase myocardial uptake of free fatty acids, glucose, lactate and triglycerides of dogs subjected to complete cardiopulmonary bypass. Carbachol was observed in the non-working dog heart to markedly reduce myocardial contractility, oxygen consumption of the heart did not undergo a decrease, indicating a dissociation between contractility and oxygen consumption. This "oxygen wasting" effect in response to parasympathetic stimulation could imply that the uptake of metabolic substrates could lead to an accumulation of lipid material in the heart. Experiments are planned to determine the concentration and turn-over rates of free fatty acid and triglyceride pools in supernatant and mitochondrial subcellular fractions of cardiac muscle. Radioactive labelled palmitic acid-1-C14 will be infused by coronary route together with carbachol for measuring turn-over rates in these fractions. Pool concentration will be determined by thin-layer chromatographic separation and analysis. In addition, glycerol concentration and intracellular myocardial lipase activity will be measured in the two subcellular fractions. While the increase in uptake of triglycerides by the heart to carbachol was found to be due to an elevated coronary flow, the possibility may also exist that the increase may also be due to a change in coronary capillary permeability. The transport of this relatively large molecule in the in situ heart will be determined by infusing dextran of different molecular sizes into the coronary arteries of the bypass animals.